4-isopropylamino-1-butanol is an important intermediate in pharmaceutical industry, and its structural formula is represented by formula (I):

4-isopropylamino-1-butanol was widely used in the pharmaceutical synthesis, for example, Patent Document WO2002088084A1 disclosed a four-step reaction using 4-isopropylamino-1-butanol as the raw material to prepare pulmonary hypertension drug of selexipag. This document was incorporated by reference into the present application.

Journal of Organic Chemistry (1961), Vol. 26, P 1744-1747 disclosed a preparation method of 4-isopropylamino-1-butanol, which comprised: (1) reacted succinic anhydride with isopropyl amine to obtain 3-isopropyl carbamoyl propionic acid; (2) reduced 3-isopropylcarbamoyl propionic acid with lithium aluminum hydride to obtain 4-isopropylamino-1-butanol.
This method had defects: lithium aluminum hydride was expensive, large consumed and high cost; lithium aluminum hydride was also a strong reducing agent with great security risks, when it meets water, explosion may be happened, so there were strict requirements for the water contents of the solvents; the yield was low; a large amount of waste water containing aluminum was produced, post-treatment was complicated, and this method was unsuitable for industrial production.
Organic and Biomolecular Chemistry (2012), Vol. 10, P 6504-6511 disclosed a preparation method of 4-isopropylamino-1-butanol, which comprised: a reduction reaction was carried out between DIBAL-H.i-PrNH2 and γ-butyrolactone in a hexane solution of diisobutylaluminium hydride (DIBAL-H) to obtain 4-isopropylamino-1-butanol. The reaction formula was shown below:

This method had defects: DIBAL-H.i-PrNH2 was needed to be prepared freshly; DIBAL-H was expensive and unstable so only its hexane solution could be used; column chromatography was used in the post-treatment; a large amount of waste water containing aluminum was produced, and this method was unsuitable for industrial production.
European Patent Document EP1400518A1 disclosed a synthesis method for 4-isopropylamino-1-butanol, which comprised: reacted 4-aminobutanol with acetone in ethanol, then kept a hydrogenation reaction at 2-3 atmospheres for 48 hours under catalyzing of platinum oxide to obtain 4-isopropylamino-1-butanol. The reaction formula was shown below:

In this process, 4-aminobutanol and platinum oxide were expensive, special high-pressure hydrogenation equipment was needed, so its industrial application was limited.
Therefore, there still had some defects in the known preparation methods of 4-isopropylamino-1-butanol in the conventional methods, it was necessary to develop novel preparation methods thereof.